3,500 research outputs found
An analysis method for time ordered data processing of Dark Matter experiments
The analysis of the time ordered data of Dark Matter experiments is becoming
more and more challenging with the increase of sensitivity in the ongoing and
forthcoming projects. Combined with the well-known level of background events,
this leads to a rather high level of pile-up in the data. Ionization,
scintillation as well as bolometric signals present common features in their
acquisition timeline: low frequency baselines, random gaussian noise, parasitic
noise and signal characterized by well-defined peaks. In particular, in the
case of long-lasting signals such as bolometric ones, the pile-up of events may
lead to an inaccurate reconstruction of the physical signal (misidentification
as well as fake events). We present a general method to detect and extract
signals in noisy data with a high pile-up rate and qe show that events from few
keV to hundreds of keV can be reconstructed in time ordered data presenting a
high pile-up rate. This method is based on an iterative detection and fitting
procedure combined with prior wavelet-based denoising of the data and baseline
subtraction. {We have tested this method on simulated data of the MACHe3
prototype experiment and shown that the iterative fitting procedure allows us
to recover the lowest energy events, of the order of a few keV, in the presence
of background signals from a few to hundreds of keV. Finally we applied this
method to the recent MACHe3 data to successfully measure the spectrum of
conversion electrons from Co57 source and also the spectrum of the background
cosmic muons
Erosion: wins races by a landslide
This model demonstrates the effects of erosion on soil. Users are able to adjust both rain (water) and wind intensity as well as rates of erosion for both. There is also an option to add different amounts of vegetative land cover; allowing users to see how areas with land cover are not as susceptible to erosion as open areas. The lesson plan has students run multiple trials, record data, create graphs and lines of best fit. The line of best fit is than used to make predictions and estimations. This was designed as a supplement to an erosion lesson and does not include all factors that affect erosion
Project of a superfluid He3 detector for direct detection of non-baryonic dark matter : MACHe3
MACHe3 (MAtrix of Cells of superfluid Helium 3) is a project of non-baryonic
Dark Matter search using superfluid He3 as sensitive medium. Simulations on a
high granularity matrix show very good rejection against background events.
First results on a prototype cell are very encouraging. Neutron detection has
been highlighted as well as cosmic muon detection. A phenomenological study has
been done with the DarkSUSY code to investigate complementarity of MACHe3 with
existing Dark Matter detectors.Comment: 5 pages, 5 figures, to appear in Proceedings of the 4th Marseille
International Cosmology Conferenc
Reflexion M\"ossbauer analysis of the in situ oxidation products hydroxycarbonate green rust
The purpose of this study is to determine the nature of the oxidation
products of FeII-III hydroxycarbonate FeII4FeIII2(OH)12CO3~3H2O (green rust
GR(CO32-)) by using the miniaturised M\"ossbauer spectrometer MIMOS II. Two
M\"ossbauer measurements methods are used: method (i) with green rust pastes
coated with glycerol and spread into Plexiglas sample holders, and method (ii)
with green rust pastes in the same sample holders but introduced into a
gas-tight cell with a beryllium window under a continuous nitrogen flow. Method
(ii) allows us to follow the continuous deprotonation of GR(CO32-) into the
fully ferric deprotonated form FeIII6O4(OH)8CO3~3H2O by adding the correct
amount of H2O2, without any further oxidation or degradation of the samples
Equilibria in Sequential Allocation
Sequential allocation is a simple mechanism for sharing multiple indivisible
items. We study strategic behavior in sequential allocation. In particular, we
consider Nash dynamics, as well as the computation and Pareto optimality of
pure equilibria, and Stackelberg strategies. We first demonstrate that, even
for two agents, better responses can cycle. We then present a linear-time
algorithm that returns a profile (which we call the "bluff profile") that is in
pure Nash equilibrium. Interestingly, the outcome of the bluff profile is the
same as that of the truthful profile and the profile is in pure Nash
equilibrium for \emph{all} cardinal utilities consistent with the ordinal
preferences. We show that the outcome of the bluff profile is Pareto optimal
with respect to pairwise comparisons. In contrast, we show that an assignment
may not be Pareto optimal with respect to pairwise comparisons even if it is a
result of a preference profile that is in pure Nash equilibrium for all
utilities consistent with ordinal preferences. Finally, we present a dynamic
program to compute an optimal Stackelberg strategy for two agents, where the
second agent has a constant number of distinct values for the items
Self-enforcing cooperation via strategic investment
We investigate how, in a situation with two players in which noncooperation is the only equilibrium, cooperation can be achieved via costly investment. We find that in the resulting equilibria, cooperation is an all-or-nothing outcome, that is, either there is full cooperation by both players, or no cooperation at all. The cost of investment is unrelated to the degree of cooperation that is ultimately achieved, unless the cost is too high, in which case investment cannot in any degree overcome the disincentive to cooperate. Moreover, the positive externalities that players have on each other in the course of play, although they affect investment, are ultimately irrelevant to the degree of cooperation achieved. We view our model as an explanation for the formation and stable existence of business alliances, where the players are firms forming a partnership defined and sustained by contractual agreements, but which is short of a merger or acquisition
MACHe3, a prototype for non-baryonic dark matter search: KeV event detection and multicell correlation
Superfluid He3 at ultra-low temperatures (100 microKelvins) is a sensitive
medium for the bolometric detection of particles. MACHe3 (MAtrix of Cells of
Helium 3) is a project for non-baryonic dark matter search using He3 as a
sensitive medium. Simulations made on a high granularity detector show a very
good rejection to background signals. A multicell prototype including 3
bolometers has been developed to allow correlations between the cells for
background event discrimination. One of the cells contains a low activity Co57
source providing conversion electrons of 7.3 and 13.6 keV to confirm the
detection of low energy events. First results on the multicell prototype are
presented. A detection threshold of 1 keV has been achieved. The detection of
low energy conversion electrons coming from the Co57 source is highlighted as
well as the cosmic muon spectrum measurement. The possibility to reject
background events by using the correlation among the cells is demonstrated from
the simultaneous detection of muons in different cells
- …